The present invention relates to a warming-up system adapted for use with a car engine, especially a gasoline engine of an automobile.
For smoother starting and more efficient warming-up of a gasoline engine at a low temperature, a richer air-fuel mixture should be supplied to combustion chambers of the engine. Therefore, a carburetor for supplying the air-fuel mixture to the combustion chambers is provided with a choke valve in the vicinity of its intake portion. The choke valve serves to constrict an air intake passage in the carburetor, thereby reducing the quantity of air fed into the combustion chambers of the engine. Thus, a rich air-fuel mixture can be fed into the combustion chambers by operating the choke valve.
The choke valve may be switched by manual or automatic remote control. When remotely operating the valve, however, it must be mechanically coupled to a manual control knob or an actuator by means of a linkage or the like. Accordingly, the mechanical arrangement surrounding the carburetor is complicated.
Conventionally known is a variable choke carburetor which does not require any choke valve. Also in the carburetor of this type, especially in starting and warming up the engine at a low temperature, a nozzle must be externally operated by means of a linkage so that the quantity of fuel injected through a main jet is increased to enrich the air-fuel mixture supplied to the combustion chambers. Requiring such a linkage, the variable choke carburetor, like the one using the choke valve, is inevitably surrounded by complicated mechanisms.
In a warming-up system using a conventional carburetor, if a throttle valve is opened to start an automobile while the engine is being warmed up, the air-fuel ratio of the air-fuel mixture supplied to the combustion chambers is lowered, causing a shortage of fuel supply to the engine. When starting the automobile in a warming-up mode, therefore, the engine hesitates to be driven, thereby lowering the running performance of the automobile. Accordingly, in the prior art warming-up system, a power jet passage is provided independently of a main jet passage in the carburetor. The power jet passage is adapted to be opened when the throttle valve is opened. When the engine shifts from warming-up mode to running mode, therefore, fuel can be injected into an intake passage through the power jet passage as well as the main jet passage. In this manner, the engine can be supplied with a necessary quantity of fuel for running. In the warming-up system with the power jet passage, however, additional elements, such as a power piston, power valve, etc., are required to operate the power jet passage as the throttle valve is opened and closed. Thus, the carburetor would be further complicated in construction.